Valencene and nootkatone are sesquiterpenes naturally found in citrus oils, such as orange and grapefruit, and other plant matter. Valencene is derived from cyclization of the acyclic pyrophosphate terpene precursor, farnesyl diphosphate (FPP), and oxidation of valencene results in the formation of nootkatone. Although both valencene and nootkatone are used as a flavorant and fragrance, nootkatone in particular is widely used in the perfume and flavor industry. Thus, among the objects herein is the provision of modified valencene synthase polypeptides and methods of using the modified valencene synthase polypeptides for the production of valencene and nootkatone.